A lithography technique comprises, for example, steps of forming a photoresist film comprising a photoresist material on a substrate, selectively exposing the photoresist film to radiation such as light, electron beam, and the like through a mask having a predetermined pattern formed thereon, and performing a development treatment to form a photoresist pattern of predetermined shape on the photoresist film. In addition, the photoresist material is referred to as a positive tone photoresist material when the portion thereof exposed to the radiation becomes soluble in a developer. And, the photoresist material is referred to as a negative tone photoresist material when the portion thereof exposed to the radiation becomes insoluble in the developer.
Recently, in the production of semiconductor devices and liquid crystal display devices, the pattern is rapidly becoming finer due to the progress in lithographic technology. As a method for fine patterning, generally, the use of a shorter-wavelength (higher-energy) exposure light source is practiced. Heretofore, ultraviolet light represented by g-line and i-line has been used but, at present, quantity production of semiconductor devices by the use of a KrF excimer laser and an ArF excimer laser has started. Further, also under study is lithography using an F2 excimer laser, an electron beam, EUV (extreme ultraviolet light), an X-ray, and the like having shorter wavelength (higher energy) than the KrF excimer laser and the ArF excimer laser.
The photoresist materials are required to have lithography characteristics such as sensitivity to these exposure light sources, resolution capability to reproduce a fine dimension pattern, and the like. As a photoresist material which satisfies these requirements, there is used a chemically amplified photoresist composition comprising a base material component which changes its solubility in an alkaline developer by the action of an acid and an acid generator component which generates an acid upon exposure.
For example, as a chemically amplified positive tone photoresist composition, there is generally used a photoresist composition comprising a resin component (a base resin), solubility of which in an alkaline developer increases by the action of an acid, and an acid generator component. When a photoresist film formed using the photoresist composition is selectively exposed to light during photoresist patterning, an acid is generated from the acid generator component in the exposed portion and, by the action of the acid, solubility of the resin in the alkaline developer increases, and the exposed portion becomes soluble in the alkaline developer.
Currently, as a base resin of a photoresist material for use in ArF excimer laser lithography and the like, the so-called acrylic resin which has a structural unit derived from a (meth)acrylic acid ester in the main chain is generally used as a polymer which is a component of the photoresist composition, because the acrylic resin has excellent transparency in the vicinity of 193 nm (see, for example, Patent Literature 1).
In addition, it is also under study to blend a nitrogen-containing organic compound such as an alkyl amine, an alkyl alcohol amine, and the like into the chemically amplified photoresist composition. The nitrogen-containing organic compound acts as a quencher to trap the acid generated from the acid generator and contributes to improvement of the lithography characteristics such as the shape of the photoresist pattern and the like. As the nitrogen-containing organic compound, a tertiary amine is generally widely used. However, as the photoresist pattern becomes finer, use of a nitrogen-containing organic compound having a carbamate group has also become known in order to improve a process margin and the like in forming an isolated pattern (see, for example, Patent Literatures 2 and 3). Furthermore, there is proposed a base resin containing, as one of the repeating units, a (meth)acrylic acid ester having a carbamate group (see, for example, Patent Literature 4).